The present invention relates to cigarettes which burn tobacco and in particular to cigarettes which, when smoked, generate low amounts of sidestream "tar" as well as sustain smolder during FTC smoking conditions.
Popular smoking articles such as cigarettes have a substantially cylindrical rod shaped structure and include a charge of smokable material such as shredded tobacco (e.g., cut filler) surrounded by a paper wrapper thereby forming a so-called "tobacco rod". It has become desirable to manufacture cigarettes having cylindrical filter elements aligned in an end-to-end relationship with the tobacco rod. Typically, filter elements are manufactured from fibrous materials such as cellulose acetate and plug wrap, and are attached to the tobacco rod using a circumscribing tipping material.
Cigarettes are employed by the user by lighting one end thereof and burning the tobacco rod. The user then receives mainstream smoke into his/her mouth by drawing on the opposite end (e.g., the filter end) of the cigarette. During the time that the cigarette is burning, sidestream smoke is generated. Sidestream smoke is smoke which directly enters the atmosphere from the lit end of the cigarette. Sidestream smoke diffuses into the atmosphere, and the characteristic visible nature thereof may be perceived negatively by certain individuals. The relative amount of visible sidestream smoke generated by a burning cigarette is related to the amount of sidestream "tar" generated by that burning cigarette. Typical cigarettes of about 84 mm length (e.g., having a tobacco rod length of about 57 mm and a filter element length of about 27 mm) often yield about 25 to about 35 mg of sidestream "tar" per cigarette. See, Proctor et al, Analyst, Vol. 113, p. 1509 (1988), for an apparatus and technique for determining the sidestream "tar" of a cigarette.
U.S. Pat. No. 4,637,410 to Luke proposes a cigarette having a circumference of from 10 mm to 19 mm. At col. 2, lines 5-7 of the reference, it is disclosed that the proposed cigarettes exhibit lower smoke component mainstream and sidestream deliveries.
U.S. Pat. No. 4,624,268 to Baker et al proposes a cigarette having wrapper paper with an inherent air permeability of 3 to 45 CORESTA units. For example, the wrapper paper is disclosed as having a coating of starch, aluminum oxide, magnesium oxide, calcium oxide, sodium formate and sodium acetate. See col. 3, lines 23-37.
U.S. Pat. No. 4,407,308 to Baker proposes a cigarette which reportedly (i) yields low sidestream smoke production upon use, and (ii) may be such as to self-extinguish when left to smolder for a prolonged period. Such a cigarette has a smokable tobacco material wrapped in a wrapper having an air permeability of not more than 3 CORESTA units.
U.S. Pat. No. 4,231,377 to Cline et al, U.S. Pat. No. 4,420,002 to Cline, and U.S. Pat. No. 4,450,847 to Owens propose that cigarette paper wrappers containing magnesium oxide and/or magnesium hydroxide materials can be used in order to manufacture cigarettes which yield reduced visible sidestream smoke during static burn periods.
It would be desirable for the cigarette manufacturer to provide a good tasting cigarette which provides good smoking satisfaction, provides low mainstream gas phase deliveries, sustains smolder during FTC smoking conditions, and which generates low levels of sidestream "tar" and hence low levels of visible sidestream smoke.